Split items/ and trainers/ into their data/ and engine/ components

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/geodude.asm

@@ -0,0 +1,10 @@
+; GeodudePokedexEntry: ; 0x1b83a1
+	db "ROCK@" ; species name
+	dw 104, 440 ; height, weight
+
+	db   "Proud of their"
+	next "sturdy bodies,"
+	next "they bash against"
+	page "each other in a"
+	next "contest to prove"
+	next "whose is harder.@"